Stable direct voltages are needed for the operation of various circuits and apparatus. The stabilization of the output voltage is in most cases effected electronically by a so-called longitudinal or a transversal regulation, or by a combination of the two methods; in all cases, however, the regulation is associated with considerable power losses.
It is also known from EP-A-0 129 181 that an inductance and a switching transistor in series and that the switching transistor may be controlled in such a manner that the peak voltages, which are produced in the inductance whenever the switching transistor is cut off and which are discharged by a diode, result in a constant direct voltage at the output. In this case however, the useful energy/input energy ratio is relatively unfavorable.